This invention relates to a device for preventing or prohibiting the use of cellular phones (or cellphones) or other devices by unauthorized individuals if they are left behind or stolen.
The number of cellphone users is increasing at a surprisingly rapid pace. Cellphones are now available in numerous different types and functions. The latest models are compact and lightweight and easy to use. Within a calling area, one can call anyone at any place through his cellphone even while he is walking, driving or in a train or a bus.
With the increase in number of cellphone users, the number of cellphones that are left behind or stolen is equally increasing. Anyone who steals or picks up someone else's cellphone may use it unlawfully. Many cellphones are thus equipped with means for prohibiting the use by such unauthorized individuals.
One such means is a system having a call prohibition mode and a means for deactivating the prohibition mode when a correct identification (ID) number is entered. Such a system is disclosed in unexamined Japanese patent publication 6-291835. This system has a personal identification number memory in which is stored a personal ID number. Only when the phone number and correct ID number are entered through input keys, is the call prohibition mode deactivated.
Another use prohibition means is disclosed in unexamined Japanese patent publication 6-326659. This means is built in a cellphone and has a receiver for receiving the phone number of the cellphone and a sub-address signal. If the receiver receives only the phone number when someone calls this cellphone, the call prohibition mode is kept deactivated, so that the call is put through. If the receiver receives both the phone number and the sub-address signal when someone, most typically the legitimate user of the cellphone, calls his own cellphone, which may have been stolen or left behind, the call prohibition mode is activated.
The former system, i.e. the ID-deactivated call prohibition system, is intended to prevent corporate employees from using corporate cellphones for private purposes. It is not intended to prohibit the use of cellphones by unauthorized individuals.
In order for a corporate employee to use a cellphone equipped with this system, he has to first connect the phone to an ID number registration device to deactivate the call prohibition mode. If the cellphone is stolen or left behind with the call prohibition mode deactivated, there is no way to prevent unauthorized use of this cellphone.
In the latter system, if the receiver receives both the phone number and the sub-address signal, the call prohibition mode is activated. The problem with this arrangement is that the call prohibition mode is kept deactivated until the receiver receives both the phone number and sub-address number. If the legitimate user notices, belatedly, the fact that his cellphone has been stolen or left behind, anyone who has the phone can use the phone freely until the call prohibition mode is activated by the user.
To solve these problems, the inventors of this application proposed in a prior patent application a call prohibition system comprising a receiver mounted in the cellphone, and a card-shaped transmitter for transmitting a radio signal. The card transmitter can be put in the user's breast pocket. If the transmitter (user) moves more than a predetermined distance away from the receiver (cellphone), a level of the signal received by the receiver from the transmitter drops below a predetermined value, and the cellphone is automatically disabled.
In this arrangement, if the user of this cellphone unknowingly leaves his phone behind or has it stolen, the phone is disabled automatically, i.e. without the need for the user to do anything.
This system has no alarm means for notifying the user of the fact that his phone has been left behind or stolen. Thus, it is possible that the user may not notice that he has lost his phone for a long time. This alarm is important because, some people who acquire the phone might decipher the use prohibition mode canceling signal from the card transmitter, or deactivate the use prohibition mode of the cellphone to use the phone without permission of the owner.
An object of this invention is to provide a use prohibition system which can disable a cellular phone or any other object if it separates more than a predetermined distance from the user, and at the same time give a warning to the user.